Post-mold cooling method and apparatus with cyclone cooling effect

ABSTRACT

A post-molding cooling apparatus directs a stream of cooling fluid against a concave interior surface of a molded article to cool the molded article. The apparatus includes an outlet positioned to direct the stream of cooling fluid into an open end of the molded article. The interior surface of the molded article is concave. The outlet is configured to direct the stream of cooling fluid in a helical direction such that at least a portion of the concave interior surface of the molded article acts as a curved surface relative to a direction of flow of the stream of cooling fluid to create turbulent flow of the stream of cooling fluid against the concave interior surface of the molded article along a length of the concave interior surface from the open end of the molded article toward a closed end of the molded article.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. app. Ser. No. 62/102,764, filedJan. 13, 2015, which is incorporated herein by reference.

FIELD

The present invention relates to cooling of molded articles.

BACKGROUND

Post-mold cooling of molded articles is well known and used becausethick walls of molded articles, such as preforms, retain heat from theinjection molding process. Preforms are usually molded from polyethyleneterephthalate (PET) resin and have wall thicknesses in the order of 2.0mm or more. Because of the resin's very poor thermal conductivity, asubstantial amount of residual heat is retained within the preform wallafter it has been ejected from the mold. This heat migrates to the innerand outer surfaces of the preform and if not removed, while the preformis held in a form, would cause the preform's surfaces to reheat to theextent that its shape would alter significantly. Further, should thepreform be touching another preform, this heat can cause them to weldtogether.

U.S. Pat. No. 4,592,719 teaches a post mold cooling device comprising atube that is inserted into a freshly molded preform. The tube extends tothe closed end of the preform such that when air is drawn through thetube ambient air is drawn into the interior of the preform from its openend causing an annular flow within the preform, the air reaches theclosed end of the tube and continues to flow within the tube to beexhausted via a conduit provided within the tubes mounting plate. Thusthe ambient air flow removes heat from the internal surface of thepreform via an annular flow stream.

U.S. Pat. No. 4,729,732 teaches a post mold cooling tube into which afreshly molded preform is inserted to continue cooling. A vacuum sourceis provided at the closed end of the tube to cause the preform to slidetoward the closed end as its outer diameter shrinks due to the cooling.The internal surface of the cooling tube is tapered to match the draftangle of the molded preform, so as the preform slides further into thetube its outer surface continues to maintain contact with the innersurface of the tube and continues to transfer heat to the cooling tube.This design was dubbed an “intimate fit” cooling tube, and is widelyused today.

U.S. Pat. No. 6,475,422 B1 teaches a cooling pin inserted into a preformwhile it is being cooled in an intimate fit cooling tube. The pin is ahollow tube that extends near to the closed end of the preform anddirects a cooling fluid (air) against the preform's inner surface at theclosed end. The fluid then forms an annular cooling stream as it movesfrom the closed end of the preform toward its open end and vents toatmosphere. This stream of annular flowing air removes heat from thepreform's inner surface.

JP 7-171888 teaches cooling the interior of a preform while it is beingcooled in a cooling tube by blowing a jet of cooling air from a nozzlespaced apart from the open end of the preform. The nozzle directing thejet of cooling air is aligned coaxially with the longitudinal axis ofthe preform and the jet of cooling air travels parallel to this axistoward the closed end of the preform. This document also teachesalternately locating the nozzle so as to direct the jet of cooling airparallel to, and along, the inner surface of the preform.

U.S. Pat. No. 6,802,705 B2 teaches cooling the external neck finish of apreform while it is being cooled in an intimate fit cooling tube. Anozzle located near the preform's open end is angled to direct a jet ofcooling air such that it flows around the thread finish formed on theexternal surface of the preform's neck portion to cool that surface. Thestream of cooling air follows the spiral shape of the thread finishflowing between, and over, the crests of the thread. There is noteaching of cooling the preform's inner surface by this means.

All these prior art examples of preform cooling, by means of directing ajet of cooling air coaxially along the preform's surface, illustratelaminar flow convection cooling.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a post-molding coolingapparatus is configured to direct a stream of cooling fluid against aconcave interior surface of a molded article to cool the molded article.The apparatus includes an outlet positioned to direct the stream ofcooling fluid into an open end of the molded article. The interiorsurface of the molded article is concave. The outlet is configured todirect the stream of cooling fluid in a helical direction such that atleast a portion of the concave interior surface of the molded articleacts as a curved surface relative to a direction of flow of the streamof cooling fluid to create turbulent flow of the stream of cooling fluidagainst the concave interior surface of the molded article along alength of the concave interior surface from the open end of the moldedarticle toward a closed end of the molded article.

The outlet can be angled. The outlet can be angled with respect to aplenum in which the outlet is disposed. The outlet can be provided in anangled nozzle that is angled with respect to a plenum.

The apparatus can further include an insert defining the outlet, theoutlet being angled.

The apparatus can further include a helical channel disposed in theinsert, the helical channel ending at the angled outlet.

The apparatus can further include a bladed insert defining an angle forthe outlet, the bladed insert being insertable into a plenum.

The apparatus can include a plurality of the outlets.

The apparatus can further include a vent tube positioned with respect tothe open end of the molded article to convey cooling fluid out of themolded article.

The vent tube can be positioned to extend into the molded article.

The apparatus can further include a cooling rod positioned to extendinto the molded article to enhance cooling of the molded article. Thestream of cooling fluid flows around the cooling rod.

The cooling rod can contain a liquid cooling circuit.

The apparatus can further include a rotary drive configured to rotatethe cooling rod to promote the turbulent flow of the stream of coolingfluid.

The cooling rod can further include external surface features to promotethe turbulent flow of the stream of cooling fluid.

According to another aspect of the present invention, a method forpost-molding cooling a molded article includes providing cooling fluidat an open end of the molded article, and helically directing thecooling fluid in the molded article such that at least a portion of aconcave interior surface of the molded article acts as a curved surfacerelative to a direction of flow of the cooling fluid to create turbulentflow of the cooling fluid against the concave interior surface of themolded article along a length of the concave interior surface from theopen end of the molded article toward a closed end of the moldedarticle.

The method can further include venting cooling fluid out of the open endof the molded article.

The method can further include positioning a cooling rod in the moldedarticle, wherein the stream of cooling fluid flows around the coolingrod.

According to another aspect of the present invention, a molded preformis provided as made according to the method.

BRIEF DESCRIPTION OF THE FIGURES

The drawings illustrate, by way of example only, embodiments of thepresent disclosure.

FIG. 1 is a diagram showing growth of a boundary layer on a flat plate.

FIG. 2 is a diagram showing thermal boundary layer development of anisothermal plate.

FIG. 3A is a diagram showing a laminar boundary layer.

FIG. 3B is a diagram showing a turbulent boundary layer.

FIG. 4A is a diagram of laminar flow within a cylinder.

FIG. 4B is a diagram of turbulent flow within a cylinder.

FIG. 5A is a diagram of Goertler vortices in a boundary layer on aconcave surface.

FIG. 5B is another diagram of Goertler vortices in a boundary layer on aconcave surface.

FIG. 6 is a diagram of span-wise distribution of a stream-wise velocitycomponent.

FIG. 7 is a diagram of Taylor vortices formed in an annulus between twocylinders in relative rotation.

FIG. 8 is a cross-sectional side view of a first embodiment of anapparatus according to the present invention.

FIG. 9 is a cross-sectional side view of a second embodiment of anapparatus according to the present invention.

FIG. 10 is a cross-sectional side view of a third embodiment of anapparatus according to the present invention.

FIG. 11 is a partial cross-sectional side view of a fourth embodiment ofan apparatus according to the present invention.

FIG. 12A is a cross-sectional side view of a fifth embodiment of anapparatus according to the present invention.

FIG. 12B is a cross-sectional rear view of the fifth embodiment of anapparatus according to the present invention.

FIG. 13A is a cross-sectional side view of a sixth embodiment of anapparatus according to the present invention.

FIG. 13B is a cross-sectional rear view of the sixth embodiment of anapparatus according to the present invention.

FIG. 14 is a cross-sectional side view of a seventh embodiment of anapparatus according to the present invention.

FIG. 15 is a cross-sectional side view of an eighth embodiment of anapparatus according to the present invention.

FIG. 16 is a partial cross-sectional side view of a ninth embodiment ofan apparatus according to the present invention.

FIG. 17 is a partial cross-sectional side view of a tenth embodiment ofan apparatus according to the present invention.

FIG. 18 is a partial cross-sectional side view of an eleventh embodimentof an apparatus according to the present invention.

FIG. 19A is a cross-sectional side view of a twelfth embodiment of anapparatus according to the present invention.

FIG. 19B is a perspective view of the insert of the twelfth embodiment.

DETAILED DESCRIPTION OF THE INVENTION

A critical factor in understanding cooling (heat transfer) by convectionis understanding the boundary layer. In fluid mechanics, a boundarylayer is the layer of fluid in the immediate vicinity of a boundingsurface where the effects of viscosity (and shear stresses) aresignificant. It is the region in which heat transfer between a fluid anda surface takes place. Friction is the primary reason for itsdevelopment.

The fundamental concept of the boundary layer was suggested by L.Prandtl (1904), and defined as a layer of fluid developing in flows withhigh Reynolds Numbers (Re), that is with a relatively low viscosity ascompared with the inertia forces. This relationship is expressed by:

${Re} = {\frac{{interial}\mspace{14mu} {forces}}{{vicsous}\mspace{14mu} {forces}} = {\frac{\rho \; {VL}}{\mu} = \frac{VL}{v}}}$

where:

V is the mean velocity of the object relative to the fluid;

L is a characteristic linear dimension (travelled length of the fluid);

μ is the dynamic viscosity of the fluid;

ν is the kinematic viscosity; and

ρ is the density of the fluid.

High Reynolds Numbers are observed when surfaces are exposed to highvelocity air streams, where within a relatively thin boundary layer,frictional shear stress (viscous shearing force) may be very large. Thisassociation is explained by:

${\tau (y)} = {\mu \frac{\partial u}{\partial y}}$

where:

τ is the frictional shear stress;

μ is the dynamic viscosity of the fluid;

u is the velocity of the fluid along the boundary; and

y is the height above the boundary.

The flow velocity (u) within the boundary layer varies from zero at thesurface (where the flow “sticks” to the wall because of its viscosity)up to the free stream velocity (within 1% error) at the outer boundaryedge (see FIG. 1). The boundary layer thickness (δ) defines the frictionforce zone, which decreases with the distance from the surface,effectively becoming inviscid (having no viscosity) at the outer edge.

In spite of its relative thinness, the boundary layer is very importantfor initiating the process of dynamic interaction between the fluid flowand the body. This interaction causes a thermal boundary layer todevelop (FIG. 2), which governs the thermodynamic interaction of heattransfer.

In FIG. 2, T∞ is the temperature of the “free flowing fluid” and Ts isthe temperature of the surface. In this case, Ts is higher than T∞, soheat will transfer by convection from the surface to the fluid.

How well the heat transfers from the surface to the fluid is a functionof the temperature profile slope through the developed boundary layer.This is expressed by the heat transfer rate equation:

q=hAΔT

where:

q is the rate of heat transfer;

h is the convective heat transfer coefficient;

A is the surface area for heat transfer; and

ΔT is the temperature difference between the surface and the fluid(T_(s)−T_(∞)).

The convective heat transfer coefficient (h) has a strong influence onthe heat transfer effectiveness, particularly when the surface area is aknown constant and the temperature differential is considered the sameas compared to similar preform molding processes.

The variable (h) can be considered as the fundamental factor foraffecting the heat transfer rate (q), and this is categoricallydependent on 1) the physical properties of the fluid and 2) the physicalsituation (flow conditions and surface geometry).

To relate this rationale to the preform post mold cooling process, thephysical properties of the fluid—air (temperature, density, thermalconductivity, specific heat capacity, and viscosity), can be consideredto be analogous cooling mediums for comparative cooling methods, and themore relevant physical situation, specifically the flow conditions andsurface geometry, can be focused on.

Fluid flow can be generalized as either laminar or turbulent. In laminarflow, as shown in FIG. 3A, the fluid moves in lamina or layers of finitespeed, with no mixing of the fluid perpendicular to the body surface,i.e., across layers. However, as inertial forces increase (via changesin the flow conditions and/or the surface geometry), the more likely thefluid flow is to become turbulent, and at a certain critical Reynold'snumber, approximately 5×10⁵ (500,000), there is a natural transitionfrom laminar to turbulent flow. Turbulent flow is less ordered withactive mixing of the fluid throughout the boundary layer, as shown inFIG. 3B.

The intense mixing of the fluid in turbulent flow increases the surfacefriction force (or drag force as it relates to surface shear stress).This enhances momentum and heat transfer between fluid particles,resulting in an increased convection heat transfer coefficient (h), andultimately an increased heat transfer rate (q).

When considering a cylindrical body (such as the interior surface of apreform), FIGS. 4A showing laminar flow and FIG. 4B showing turbulentflow illustrate the differences between the two conditions.

Both conditions will remove heat from the surrounding body, but theturbulent flow is profoundly more effective than the laminar flow. Withlaminar flow, the layers nearest the surface are in direct contact withthe heat that needs to be removed, but these layers are highly orderedand move slowly (due to friction), therefore the heat transfers slowlyto the faster moving inner layers. The layers closest to the center,which are moving fastest, receive very little heat.

With turbulent flow, the fluid is constantly being tumbled and mixed. Itis highly irregular and characterized by random three-dimensionalmotions of fluid particles. Mixing within the boundary layer carrieshigh speed fluid toward the surface and transfers slower moving fluidfarther into the free stream. Essentially, more of the fluid would comeinto contact with the body surface, all of which would be used to removeheat from the body. This is the desired effect.

With preform post mold cooling processes, turbulent air flow, and morespecifically high surface shear stress, is not easily achieved withtypical parallel or annular air streams. Furthermore, the interiorsurface geometry of freshly molded preforms cannot be physically alteredto increase the level of turbulence/surface shear stress. However, byutilizing a unique method of directing an air stream across the interiorpreform surface in a spiral/corkscrew (helical) direction, itessentially causes the interior body of the preform to become a curved /concave surface relative to the direction of the air stream.

The concave surface (now physically exploited with the helical airstream) causes the laminar air flow to transform into a non-uniformthree-dimensional pattern, where a turbulent cyclonic centrifugalinstability occurs, resulting in the occurrence of stream-wisecounter-rotating Goertler vortices (named after Goertler, 1940) as shownthree-dimensionally in FIGS. 5A and 5B.

The centrifugal force (the reaction force that is caused by thecentripetal acceleration that keeps the air moving along a curved path)is inversely proportional to the surface radius, making it extremelyeffective for use with preforms, as they typically have small internaldiameters (radii). This force also increases as the square of thetangential velocity, producing a massive wall shear effect. Theintensified wall shear decelerates the boundary layer air as it flowsaround the concave surface, creating an unstable situation. The fluid inthe inside lanes, with the smaller radius (away from the concave wall),moves faster than that of the fluid near the surface with the largerradius (against the concave wall). This causes the fluid furthest awayfrom the wall to move outward towards the wall, to forcibly exchangeplaces with the fluid near the wall. This sets up a system of counterrotating vortices, whose axes of rotation are parallel to the wall butperpendicular to the main flow direction.

This centrifugal effect is re-illustrated two-dimensionally in FIG. 6.The boundary layer flow is characterized by down-wash regions, where thehigh speed free stream fluid is swept towards the concave surface, andup-wash regions, where low speed fluid is convected away from thesurface, resulting in a wavy fluid distribution in the span-wisedirection, within the stream-wise fluid flow path. This highly dynamiceffect has an intense impact on the surface turbulence/shear stress,resulting in an elevated heat transfer rate.

In addition, Liepmann (1945) found that the boundary layer transitionfrom laminar flow to turbulent flow on a concave surface occurred at aReynolds Number much lower than on a flat surface. As such, lowerinertial forces are needed to produce an effective heat transfer rate,resulting in a more efficient use of an air source.

This phenomenon can be augmented further by placing a cylindrical objectinside the concave cylindrical body, where the two surfaces (concave andconvex) induce spontaneous air stream flows, causing shear stressintensification within the boundary layer.

A similar effect can also be achieved with the sole rotation of theinside cylinder (that is without the introduction of a forced airstream), where the creation of a steady and smooth circular fluid motion(Couette flow) becomes unstable when the angular velocity of the innercylinder is increased above a certain threshold, thus generating Taylorvortices (essentially the same Goertler ring vortices although ascreated in the annulus between the concentric cylinders), as shown inFIG. 7.

When combining the effects of the rotating inside cylinder with thecyclone forced helical air stream in the corresponding (or opposite)rotationally angled direction, immense levels of instableturbulence/wall shear can be produced. A further improvement to thisconfiguration would be to add geometrical surface features and/orsurface textures to the inside cylinder to generate even higher levelsof turbulence. Incorporating an external cooling medium, for examplechilled water, to the inside cylinder, would further benefit the processby raising the convective heat transfer coefficient (h).

In recognizing these phenomena, mechanisms have been designed to realizeboth:

(1) Improved cooling performance of the interior surface of freshlymolded preforms during the post mold cooling process, and

(2) Minimized/optimized use of air as the cooling medium to yield alower cost heat removal medium.

FIG. 8 shows a section view of the first embodiment, in which a preform10 is arranged in a post-molding configuration and supported by anymeans known to those practicing the art. The preform 10 is spaced apartfrom a plate, or plenum, 20 containing a source of cooling fluid, suchas air under pressure 30. An angled outlet or orifice 40 is positionedsuch that a stream of cooling fluid 50 is directed into the interior 60of the preform 10. The direction is both tangential and on an inclinedplane to cause the stream of cooling fluid to flow in a helical patternagainst the concave interior surface of the preform 10 substantiallyalong its length. Ideally, a series of Goertler vortices are created inthe boundary layer optimizing the heat transfer from the preform'sinterior surface to the stream of cooling fluid. The heated coolingfluid 80 is displaced from the preform's interior via gap 70 by thecontinuing stream of fresh cooling fluid 50 flowing into the preform.

The plenum 20 can include any combination of mold plates and mechanismsto hold one or more preforms 10 relative to the plenum 20 duringcooling. The plenum 20 may be part of an injection molding system, apreform handling or cooling system, or similar. One or more angledoutlets 40 may be provided to the plenum 20 or to one or more insertsattached to or within the plenum 20.

FIG. 9 shows a section view of the second embodiment in which the angledoutlet is mounted on the plate's surface in an adjustable nozzle 100allowing the orientation of the outlet to be altered and optimized. Theother features and aspects of this embodiment are similar or identicalto the first embodiment, with like reference numerals denoting likeparts.

FIG. 10 shows a section view of the third embodiment in which two ormore angled outlets 140 and 150 are provided in order to increase theflow rate of the cooling fluid and provide better coverage of the insidesurface area of the preform, thereby increasing the rate of heat removalfrom the preform's internal surface. The drawing shows two angledoutlets, however additional outlets may be used to enhance performance.The outlets 140 and 150 are aimed to provide the same sense of angularmotion (clockwise or counter-clockwise) to the incoming air streams. Theother features and aspects of this embodiment are similar or identicalto the first embodiment, with like reference numerals denoting likeparts.

FIG. 11 shows a section view of the fourth embodiment in which a venttube 180 is provided such that the heated cooling fluid 80 is venteddirectly from the closed end of the preform 10. The vent tube 180conveys the heated cooling fluid through the plate, or plenum 20, andexhausts it beyond. The other features and aspects of this embodimentare similar or identical to the first embodiment, with like referencenumerals denoting like parts.

FIGS. 12A and 12B show section views of the fifth embodiment in which amultiport spigot 200 is provided comprising a central vent tube 210 thatpasses through the plate, or plenum 20 to exhaust the heated coolingfluid beyond, and surrounding the central vent tube 210, multiple angleoutlets 220 connected via annular channels 230 to the source ofpressurized cooling fluid 30 in the plate, or plenum 20 such thatmultiple streams of cooling fluid are directed against the interiorconcave surface of the preform substantially along its length. Thespigot size and position can be changed to enter further into thepreform interior to obtain the desired effect. The other features andaspects of this embodiment are similar or identical to the firstembodiment, with like reference numerals denoting like parts.

FIGS. 13A and 13B show section views of a sixth embodiment in which astatic multi-bladed insert 300 is used to cause the cooling fluidstream, supplied via annular pathway 310, to be directed against theinterior concave surface of the preform substantially along its length.A central vent tube 320 is provided that passes through the plate, orplenum 20 to exhaust the heated cooling fluid beyond. The other featuresand aspects of this embodiment are similar or identical to the firstembodiment, with like reference numerals denoting like parts.

FIG. 14 shows a section view of a seventh embodiment in which a centralcooling rod 400 is inserted into the preform. The cooling rod 400 andthe other cooling rods discussed in other embodiments may be hollow witha closed end, or may be solid, and may be termed a “cooled core”. Inthis embodiment, cooling rod 400 contains a water cooling circuit 410that is supplied by an infeed channel 420 and an exit channelincorporated in the plate, or plenum 440. The length of the cooling rod400 is long enough to reach the proximity of the closed end of thepreform. The rod is surrounded by a cladding of geometrical surfaces orsurface textures 460 to enhance the promotion of turbulent flow of thecooling fluid stream 450 supplied via angled outlets 470. The surfacetexture 460 can be a polished surface, a golf ball texture, a roughsurface, a grooved surface, or the like, or any combination thereof. Theother features and aspects of this embodiment are similar or identicalto the first embodiment, with like reference numerals denoting likeparts.

FIG. 15 shows a section view of the eighth embodiment in which thecentral cooling rod of FIG. 14 is provided with a rotary drive 500comprising a belt/chain 510 that engages a pulley/sprocket 520 attachedto the cooling rod 530. Driving the belt/chain 510 causes the coolingrod 530 to rotate. Rotation of the cooling rod 530 further helicallydirects the flow of cooling fluid to enhance the promotion of turbulentflow of the cooling fluid stream 540 supplied via the angled outlets550. The rotary drive 500 can also be run by rack/gear or direct drivemechanisms. A sealing and rotating coupling is provided between therotating cooling rod 530 and the non-rotating cooling fluid channels.The other features and aspects of this embodiment are similar oridentical to the seventh embodiment, with like reference numeralsdenoting like parts.

FIG. 16 shows a section view of the ninth embodiment in which thecooling fluid stream and angled outlets of the earlier embodiments arenot used. The rotating cooled rod of FIG. 15 has been retained and itsrotary motion and external cladding of geometrical surfaces or surfacetextures 460 alone direct the helical flow in the annular space betweenthe inner surface of the preform and the exterior surface of the coolingrod to generate turbulence and enhance the transfer of heat from thepreform to the cooling fluid flowing through the cooling rod. The otherfeatures and aspects of this embodiment are similar or identical to theeighth embodiment, with like reference numerals denoting like parts.

FIG. 17 shows a section view through the tenth embodiment in which theconfiguration shown in FIG. 16 is further enhanced by the addition ofexternal surface features 600 that can be configured as fins, spirals,wings, pineapple studs, or the like, or combinations thereof to furtherenhance the helical flow to promote turbulence and improve the transferof heat from the preform to the cooling fluid flowing through thecooling rod. The other features and aspects of this embodiment aresimilar or identical to the ninth embodiment, with like referencenumerals denoting like parts.

FIG. 18 shows a section view of an eleventh embodiment in which acentral cooling rod 700 is inserted into the preform 10. The cooling rod700 is affixed to the plenum 20 and may be solid or may have an interiorvoid. The length of the cooling rod 700 is long enough to reach theproximity of the closed end of the preform 10. One or more angledoutlets 40 are provided in order to introduce a helical stream ofcooling air. The cooling rod 700 may be surrounded by a cladding ofgeometrical surfaces or surface textures to enhance the promotion ofturbulent flow of the cooling fluid stream supplied via angled outlets.The surface texture can be a polished surface, a golf ball texture, arough surface, a grooved surface, or the like, or any combinationthereof. The other features and aspects of this embodiment are similaror identical to the first embodiment, with like reference numeralsdenoting like parts. For example, the cooling rod 700 can be configuredto be driven to rotate, as in other embodiments discussed herein, suchas the eighth embodiment (FIG. 15).

FIGS. 19A and 19B show a twelfth embodiment in which an insert 800 isprovided within a spigot 802 that extends into the preform 10. Theinsert 800 includes one or more external helical channels 804 formed inits outside surface 806. Pressurized cooling fluid 30 is provided by afeed channel 808, which receives cooling fluid from a source, such asthe plate or plenum (not shown) discussed in other embodiments. Coolingfluid is conveyed through the spigot 802 to the outside surface 806 ofthe insert 800 whose helical channels 804 shape the flow of coolingfluid into a helical path. Each helical channel 804 ends at an angledoutlet 810 from which jets cooling fluid in a helical stream 50 thatexits the spigot 802 and enters the preform 10. The helical streams 50of cooling fluid cool the preform 10. The insert 800 has a centralexhaust channel 812 for exhausting heated cooling fluid beyond. Thepositions and sizes of the spigot 802 and insert 800 can be changed andthe shape, size, and number (e.g., 1, 2, 3, 4, etc.) of helical channels804 can be changed to obtain the desired effect. The other features andaspects of this embodiment are similar or identical to the firstembodiment, with like reference numerals denoting like parts.

In various embodiments above, suction can be used, instead of or inaddition to positive pressure, to impart motion to cooling air. This canbe done with or without sealing the preform to the plate. It iscontemplated that suction results in flow that is lessdirectional/controllable, hence a contoured spiral surface or othersurface feature (e.g., see FIG. 17) may be provided to draw the airstream into a suitable helical path.

The above techniques may provide for improved cooling performance, whichresults in a higher production rate. Further, optimized use of air maybe realized, resulting in lower levels of air usage which can translateinto a cost reduction. Moreover, the above techniques may result inreduced crystallization in molded articles/preforms, resulting in betterblow molding performance, reduced stress, and better aesthetics. Otheradvantages may also be apparent to those of ordinary skill in the art.

What is claimed is:
 1. A post-molding cooling apparatus configured to direct a stream of cooling fluid against a concave interior surface of a molded article to cool the molded article, the apparatus comprising an outlet positioned to direct the stream of cooling fluid into an open end of the molded article, the interior surface of the molded article being concave, the outlet being configured to direct the stream of cooling fluid in a helical direction such that at least a portion of the concave interior surface of the molded article acts as a curved surface relative to a direction of flow of the stream of cooling fluid to create turbulent flow of the stream of cooling fluid against the concave interior surface of the molded article along a length of the concave interior surface from the open end of the molded article toward a closed end of the molded article.
 2. The apparatus of claim 1, wherein the outlet is angled with respect to a plenum in which the outlet is disposed or the outlet is provided in an angled nozzle that is angled with respect to a plenum.
 3. The apparatus of claim 1, further comprising an insert defining the outlet, the outlet being angled.
 4. The apparatus of claim 3, further comprising a helical channel disposed in the insert, the helical channel ending at the angled outlet.
 5. The apparatus of claim 1, further comprising a bladed insert defining an angle for the outlet, the bladed insert being insertable into a plenum.
 6. The apparatus of claim 1, comprising a plurality of the outlets.
 7. The apparatus of claim 1, further comprising a vent tube positioned with respect to the open end of the molded article to convey cooling fluid out of the molded article.
 8. The apparatus of claim 6, wherein the vent tube is positioned to extend into the molded article.
 9. The apparatus of claim 1, further comprising a cooling rod positioned to extend into the molded article to enhance cooling of the molded article, wherein the stream of cooling fluid flows around the cooling rod.
 10. The apparatus of claim 8, wherein the cooling rod contains a liquid cooling circuit.
 11. The apparatus of claim 8, further comprising a rotary drive configured to rotate the cooling rod to promote the turbulent flow of the stream of cooling fluid.
 12. A method for post-molding cooling a molded article, the method comprising: providing cooling fluid at an open end of the molded article; and helically directing the cooling fluid in the molded article such that at least a portion of a concave interior surface of the molded article acts as a curved surface relative to a direction of flow of the cooling fluid to create turbulent flow of the cooling fluid against the concave interior surface of the molded article along a length of the concave interior surface from the open end of the molded article toward a closed end of the molded article.
 13. The method of claim 12, further comprising venting cooling fluid out of the open end of the molded article.
 14. The method of claim 12, further comprising positioning a cooling rod in the molded article, wherein the cooling fluid flows around the cooling rod.
 15. A molded preform made according to the method of claim
 12. 